Repair Log: Sharp Twin Famicom

[TrekkiesUnite118]

The Twin Famicom has AV Out though.

[Guntz]

JP RF does work on US TVs, you just have to find one that goes up to channel 95, or somewhere around there. The problem is most US TVs don't go that high.

[TrekkiesUnite118]

Also for the original Famicom doesn't it require a special RF box? I've heard tracking those down can be a bit of a pain.

I've also heard the RF quality of the original Famicom is pretty awful, about on par with the top loader NES due to the lack of RF shielding in the system and because the boards are laid out in a similar manner apparently.

[ApolloBoy]

Also for the original Famicom doesn't it require a special RF box? I've heard tracking those down can be a bit of a pain.

Nope, the Famicom can use the NES switchbox or you can use an RCA-to-coax adapter. The Twin Fami and the AV Fami require external RF modulators however.

...except if I were to have an original-model Famicom. If I get one, I WILL NOT A/V mod it like I did with my Top-Loader NES (I couldn't stand its crappy RF anymore), and if an A/V mod was done on the system, I would undo it. I'm dead serious when I say this.

Why? The Famicom's RF is terrible and full of vertical lines like the top loader, why on earth would you undo a pre-existing AV mod?

[Ace]

Why? The Famicom's RF is terrible and full of vertical lines like the top loader, why on earth would you undo a pre-existing AV mod?

Is it really that bad? If that's the case, I'd just build a new video amp, and I will undo an A/V mod because I DO NOT want a modified Famicom. Before I got my Twin Famicom, I was thinking of getting an original-model Famicom and avoided all systems with A/V mods that look irreversible (by that, I mean there were holes drilled into the Famicom's case), until I discovered the HVC-CPU-GPM motherboards. Those have excessively loud expansion audio much like the AV Famicom, which, for me, is unacceptable.

Personally, though, I see no reason for an original-model Famicom. With the Twin Famicom, the original model is pointless.

[ApolloBoy]

Is it really that bad? If that's the case, I'd just build a new video amp, and I will undo an A/V mod because I DO NOT want a modified Famicom. Before I got my Twin Famicom, I was thinking of getting an original-model Famicom and avoided all systems with A/V mods that look irreversible (by that, I mean there were holes drilled into the Famicom's case), until I discovered the HVC-CPU-GPM motherboards. Those have excessively loud expansion audio much like the AV Famicom, which, for me, is unacceptable.

All three original Famicoms I've owned had bad RF, though the one I own now is the only one I've AV modded. I never had a problem with the expansion audio either, in fact I think it's too quiet on the AV Fami. Even so, the difference is still pretty insignificant and is certainly not a reason why I'd rule out the original Fami.

Also, you know there are easily reversible AV mods for the Fami, right? Those just use hardwired cables routed through the controller cable holes.

[TrekkiesUnite118]

Couldn't you just replace the RF connector with some kind of AV connector so you could just plug in an AV cable? For example you could replace it with the same Mini DIN the Genesis 2 uses and wire it up the same, then use your Genesis AV cables for the Famicom. That wouldn't require dramatic alterations to the case and you'd get AV out. Or you could just remove the RF connector and have a hardwired AV cable come out that hole. That would probably look decent too if done right, and it would be naturally fitting with the original Famicom with the hardwired controllers and all.

As for the Expansion Audio being louder than the Famicom Audio, isn't that the case with all Famicoms?

[Ace]

As for the Expansion Audio being louder than the Famicom Audio, isn't that the case with all Famicoms?

That's only partially correct. The sound out of the Famicom Disk System's RAM cartridge is quieter than the 2A03, but on some Famicom revisions, it's about the same volume as the 2A03, but other sound chips like Konami's VRC6 are loud no matter what (though the VRC6 makes the 2A03 almost inaudible on the AV Famicom). Watch this video on NicoNicoDouga comparing expansion audio on different revisions of the Famicom using the Famicom Disk System: http://nicoviewer.net/sm16346242

Make sure you just click the Play symbol and let NicoViewer do the rest, otherwise, you'll be redirected to NicoNicoDouga and won't see the video.

You'll see when the Famicom revision hits HVC-CPU-GPM-01 up to HVCN-CPU-02 (2nd revision of the AV Famicom), the audio out of the Disk System is much louder than on revision HVC-CPU-08 and earlier. And the sound out of the AN-500R Twin Famicom (the red one) is the worst of all the Famicoms shown.

[80sFREAK]

JP RF does work on US TVs, you just have to find one that goes up to channel 95, or somewhere around there. The problem is most US TVs don't go that high.

Not high, actually, it's right between VHF and UHF.

2 ApolloBoy "Jail bars" have nothing to do with RF output, it's another story.

[ApolloBoy]

2 ApolloBoy "Jail bars" have nothing to do with RF output, it's another story.

I'm aware of that, but the bad RF quality doesn't help matters.

[Ace]

Nothing new to repair the system, but I at least have a temporary way of playing Famicom Disk System games on the Twin Famicom using this computer:



It's a Prosys computer sporting a 450MHz Pentium III and running on Windows 95 which I boot to MS-DOS every now and then. This computer is linked to the Twin Famicom via this cable:



It's a custom FDSLoadr cable meant to plug into one of the Twin Famicom's expansion ports. If you were to flip over the Twin Famicom, you'll see this cover (picture's a bit blurry, but you can still see the cover):



Popping off this cover reveals expansion ports C and D linked via a cable:



Wouldn't you know it, these ports are direct connections to the Disk System hardware in the Twin Famicom. Expansion port C links to the RAM cartridge hardware much like the cable on a RAM cartridge for a standalone Disk System while expansion port D links directly to the disk drive.

Now to get a Disk System game loaded. Here's the custom cable plugged into expansion port C:



And into the computer:



Now, here's everything booted up and ready to go (another blurry image):



After typing up a command in DOS, the Twin Famicom loads the game being transferred into the console by FDSLoadr:



Finally, the main game I wanted to get a Disk System or Twin Famicom for is loaded:



Falsion. I'm terrible at it, but I really like this game.

Of course, I will get actual Disk System games once the disk drive is repaired. This is only temporary, though if I do end up with a dead disk, I'll try to use FDSLoadr to recover the disk.

At the same time, I've come to the conclusion the audio circuitry needs a bit of work. The audio is WAY too heavily low-pass filtered, resulting in muffled sound (the bass is good, but the treble is very weak), and on top of that, not only is the FM Synthesis out of the 2C33 as loud as on a Famicom with HVC-CPU-GPM-0x motherboards and on the AV Famicom (surprising considering the only Twin Famicom with major sound issues is the AN-500R model, and even then, not all of them have distorted sound or a VERY loud 2C33), but the output levels aren't the same when the console is in disk mode or cartridge mode. In cartridge mode, the audio is quiet, forcing me to set the volume on my TV to 10 (typical listening level when an audio signal is weak), but in Disk System mode, the audio is as loud as my Front-Loader NES, so to hear everything at a proper volume, my TV's volume is set to 9, the volume setting it's set to for the majority of consoles I hook up to the TV (and for normal TV). So, the to-do list is as follows:

1) Get a Disk System game and a drive belt to fix the disk drive
2) Reduce the volume of the 2C33's FM Synthesis
3) Locate and remove the low-pass filter making the audio as muffled as it is
4) Increase the volume of the Twin Famicom's audio output in cartridge mode

[Ace]

New update.

I stopped by a local electronics shop with the Twin Famicom's disk drive and ended up getting a belt for it:



It's a bit hard to see, but you can tell there is now a belt on the drive (no more of that mush). However, I still don't know if the belt is 100% adequate for the drive as yes, the head moves, but as I still don't have any physical Disk System games, I don't know if the drive will read disks with this belt or fail and give error after error.

I've also taken a look at the Twin Famicom's audio circuitry, and holy crap, is it disorganized! I got lost so many times while trying to retrace the circuit. Still, I managed to find out why the sound is so heavily muffled. The culprit:



Capacitor C205 on the power board, indicated by the red box and arrow. Normally, there would be a 0.022uF ceramic capacitor here which low-pass filters the audio like crazy, resulting in very muffled sound. I'm not too fond of muffled NES audio, so I removed the cap, and wow, there's a HUGE difference in the clarity of the audio output. Why Sharp put this cap there, I have no idea.

Here's an archive with 4 audio samples from Akumajou Densetsu and The Legend of Zelda: http://www.4shared.com/zip/Cgku1xOO/...mples_wit.html

This will show you the difference between having that low-pass filter cap and not having the cap. All audio samples have also been amplified by 10dB in Audacity so you can hear the difference in audio levels when the system is in disk mode and cartridge mode.

Now, the to-do list is as follows:

1) Get a Disk System game to test the drive
2) Find out how to lower the volume of the 2C33's FM Synthesis
3) Increase the volume of the console's audio output in cartridge mode (may require an op-amp if there's no amplification being done after the audio passes through the cartridge slot)

[eddiespruce]

Seeing that you're aiming to get some Disk System games, I highly recommend "Ai Senshi Nicol". It's a fun game by Konami that never made it to the U.S.

[Ace]

Huh... I think I may enjoy this game. I'll definitely give it a shot.

[ApolloBoy]

I just took a look at my Twin Fami Turbo and it has the same 0.022 uF capacitor for audio like the original does, even though the power board has a different layout. I'm going to try removing it and see how it goes.

EDIT: Clipped off the cap and the audio does indeed sound a lot better! Thanks!